There are left-side side levers. On this site one gentleman opined that the right-side side lever was easier for a shooter. . .the left-side for a loader. Probably it was just the choice of the person who ordered it. I will say my side-lever Reilly is really easy to break and load. I would imagine that you would want that lever pointed away from your face though.

This Reilly was owned by Terry Buffum; SN 17392 (1871):
https://www.amoskeagauction.com/110/132.php
[Linked Image from jpgbox.com]